2. Drugs for Pain, Headache, and Anesthesia
Chapter 9
Drugs for Pain, Headache, and Anesthesia
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Topics
Anatomy and Physiology of Pain and Sensation
Headache
Anesthesia
Analgesic and Anesthetic Antagonists
Herbal and Alternative Therapies
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4. Anatomy and Physiology of Pain and Sensation
About Pain
Is a physiological response to stimuli and is usually associated with tissue damage
Peripheral nervous system
Detects temperature, touch, and pain
Is also responsible for the five senses
Sensation
Heat, cold, pressure, or chemical stimulus is perceived by sensory receptors and nerve endings in the peripheral nervous system
Signals travel up the spinal cord to the cerebral cortex and sensation is perceived
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5. Anatomy and Physiology of Pain and Sensation
Anatomy of the Nervous System
Pain alerts the body to harmful injury or inflammation
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6. Anatomy and Physiology of Pain and Sensation
Inflammation
Causes the release of arachidonic acid, which is acted upon by the enzyme cyclooxygenase to form prostaglandins
Prostaglandins
Are chemical triggers for pain and cause local redness and swelling
Are pyrogens (substances that produce fever)
Acute pain
Response involves the sympathetic nervous system
Pulse increases, blood pressure rises, breathing speeds up, muscles tense, and pupils dilate
Other responses: altered stomach and bowel functions, impaired immune response, and water retention
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7. Anatomy and Physiology of Pain and Sensation
The Inflammation Process: Acute Pain
Inflammation or harmful injury causes a cascade of events
Some pain medications treat pain and fever by inhibiting prostaglandin production
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8. Anatomy and Physiology of Pain and Sensation
Chronic Pain
Lasts longer than 3 months
Produces a compensatory response involving depression and behavioral adaptation over time
Causes feelings of hopelessness, sleep disturbances, lack of facial expression, isolation, fatigue, anger, and physical inactivity
Usually coexists with other conditions
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9. Anatomy and Physiology of Pain and Sensation
Somatic and Visceral Pain
Somatic pain
Occurs from injury to the body frame, such as to bones and muscles
Visceral pain
Occurs from problems with internal organs, such as the kidneys or intestines
Symptoms include nausea, vomiting, and sweating
Patients may also describe the pain as originating somewhere else in the body (referred pain)
An example is pain in the left shoulder and arm that accompanies a heart attack
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10. Anatomy and Physiology of Pain and Sensation
Neuropathic Pain
Occurs from damage to nerve tissue itself
Symptoms include tingling, burning, or stabbing pain in the area of injury
Often involves the sciatic nerve in the legs, the trigeminal nerve in the face, and the peroneal nerves in the feet
May not respond to typical analgesics
Other agents (antidepressants or anticonvulsants) that alter nerve signal transmission are used
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11. Anatomy and Physiology of Pain and Sensation
Sympathetically Mediated Pain
Is associated with nerve overactivity
Patient feels pain when no obvious stimulus exists
Phantom limb pain
Patient feels pain in a missing limb
Treat with nerve-blocking agents
Impact of Pain
Can hugely impact a patient’s quality of life and health
Pain treatment involves good assessment, along with realistic and appropriate expectations for treatment
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12. Anatomy and Physiology of Pain and Sensation
Drugs for Pain
Mild pain
Is managed with OTC analgesics (drugs that treat pain)
Moderate to severe pain
Requires prescription medications; many are narcotics
Narcotic analgesics
Are natural (e.g., codeine, morphine) or synthetic drugs with morphine-like activity
Are controlled substances
Opiates
Can cause dependence, leading to addiction
Produce euphoric effects that mimic endorphins, which help the body deal with pain
over-the-counter (OTC)
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13. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Tolerance and Dependence
Tolerance
Is a process whereby the body becomes less sensitive to the effects of a drug over time
Requires higher and higher doses to produce the same therapeutic effects
Dependence
Can be both physiological (physical) and psychological (emotional)
May need medical assistance to stop therapy
Tapering (reducing doses over time) may avoid or minimize withdrawal symptoms
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14. Anatomy and Physiology of Pain and Sensation
Physiological Dependence
The body becomes used to the effects of a drug over time and physically adjusts
When drug use stops, uncomfortable and sometimes life-threatening withdrawal symptoms occur
Many drugs besides narcotics can cause this, such as blood pressure medications
Psychological Dependence
The euphoric effects and relief a patient feels when analgesia for pain occurs
It does not always lead to addiction
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15. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Addiction
Is a compulsive behavioral disorder in which the patient becomes preoccupied with drug use
Addicts
No longer take the drug as instructed
Display decreased general function and ability to participate in normal life
Alter normal behavior to get more of the drug and may see multiple prescribers and pharmacies
Will likely need counseling and medical treatment
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16. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Addressing Addiction
Fear of addiction is a major barrier to adequate pain control
Technicians
Can help patients to understand tolerance and dependence effects in opiate drug use
Some patients believe tolerance and dependence are addiction, so they resist appropriate therapy
Can alert pharmacists when psychological dependence and addiction may be developing
Important for patient safety
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17. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Acetaminophen
Indications: mild pain and fever
Especially good for pain with headache or OA and for children who have pain or fever
Indications (other): in combination with opiates for moderate to severe pain
Achieves synergistic therapy
Smaller doses needed and fewer side effects occur than by using either agent alone
Mechanism of Action: inhibits prostaglandin production in the CNS
osteoarthritis (OA)
central nervous system (CNS)
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18. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Acetaminophen (continued)
Is not an anti-inflammatory (unlike NSAIDs)
Routes: oral
Side Effects: stomach upset and excitation
Cautions
Can cause liver toxicity if taken in high doses (4 g a day) or used chronically at daily maximum dose levels
If regular alcohol use, total daily dose should be limited to 2 g due to possible serious liver damage
Take in the lowest doses possible for short-term use
nonsteroidal anti-inflammatory drugs (NSAIDs)
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19. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Aspirin
Indications: mild to moderate pain and fever; especially useful for pain with inflammation such as OA
Indications (low dose): stroke and heart attack prevention
Indications (other): in combination with opiates for moderate to severe pain through synergistic therapy
Mechanism of Action: inhibits cyclooxygenase, the enzyme that converts arachidonic acid to prostaglandins
Routes: oral; also rectal
Side Effects (common): GI irritation, erosion, and bleeding; headache; dizziness; and rash
gastrointestinal (GI)
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20. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Aspirin (continued)
Side Effect (severe): aspirin toxicity, which includes ringing in the ears (tinnitus), dizziness, and confusion
Cautions
Do not use if at risk for bleeding, have gout, or ulcers
Do not use if have asthma or are pregnant
Do not use if have allergy to aspirin
Do not use in children for fever or pain
Associated with Reye’s syndrome
Do not take with NSAIDs because it increases bleeding risk and decreases aspirin effectiveness
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Your Turn
Question 1: A patient who has osteoarthritis in both knees is having difficulty sleeping, feels tired and hopeless, and is physically inactive. What could cause this to happen? Answer: The patient has chronic pain and is responding with depression and behavioral changes. Question 2: What is the reason aspirin should not be taken with NSAIDs? Answer: Aspirin taken with a NSAID can increase the risk of bleeding risk. In addition, the effectiveness of aspirin is decreased.
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22. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: NSAIDs and COX-2 Inhibitors
Indications: mild to moderate pain and fever
Especially useful for pain with inflammation such as injuries and some forms of arthritis
Indications (some NSAIDs): combined with opiates for moderate to severe pain through synergistic therapy
Mechanism of Action (NSAIDs): inhibit cyclooxygenase I and II
Mechanism of Action (COX-2 inhibitors): inhibit cyclooxygenase II
cyclooxygenase-II (COX-2)
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23. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Narcotic Analgesics
Most are opiate derivatives similar in action to morphine
Indications: moderate to severe pain; used alone or in combination with other analgesics
Mechanism of Action: inhibit mu and kappa opioid pain receptors
Indications (methadone): severe pain and drug abuse treatment
Indications (tramadol): short-term treatment (five days or fewer) of moderate to severe pain
Tramadol is used when side effects of opiates are intolerable or addiction potential is high
intramuscular (IM)
intravenous (IV)
subcutaneous (SC)
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24. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Narcotic Analgesics (continued)
Routes: all are oral; some are IM, IV, SC, and IT
Side Effects (common): sedation, dizziness, stomach upset, fatigue, headache, and constipation
Side Effects (less common): changes in blood pressure and heart rate
Side Effect (severe): respiratory depression, especially at high doses; tolerance to this effect may develop at higher doses
Side Effects (other): dysphoria (not euphoria), nausea, and vomiting
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25. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Narcotic Analgesics Cautions
Causes drowsiness and fatigue
Are controlled substances and have legal restrictions on handling and dispensing
Do not use with alcohol
Oxycodone (OxyContin) and oxymorphone (Opana)
Are for chronic pain, especially for malignant pain
Do not crush or chew extended-release form
Tramadol
Can lower seizure levels
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26. Anatomy and Physiology of Pain and Sensation
Drugs for Pain: Neuropathic Pain Agents
Neuropathic pain
Does not always respond to conventional analgesics
Gabapentin (anticonvulsant) and tricyclic antidepressants (such as amitriptyline and nortriptyline)
Are often used for neuropathic pain
Indications (long-term, take at bedtime): spinal cord injury, sciatica, trigeminal neuralgia, and diabetic peripheral neuropathy
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Headache
Headaches
Are a specific type and location of pain that are very common and affect millions of patients in the U.S.
Migraine Headaches
Are characterized by a throbbing, unilateral pain in the head that impacts normal activity of life
Possibly caused by cerebral surface blood vessels constricting and then rapidly dilating
Serotonin, a potent vasoconstrictor and neurotransmitter, may be involved
United States (U.S.)
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Headache
Migraine Headaches (continued)
Involve pain, nausea, vomiting, and/or sensitivity to light and sometimes to sound
Occur with or without aura
Involves vision disturbances, such as seeing halos, flashing lights, floating spots, or areas of darkness or blurriness
Is part of the prodrome (early) phase of a migraine
Is a warning for patients to seek immediate treatment
Treatment
Is acute pain medication and abortive therapies
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Headache
Migraine Headaches (continued)
Prevention
Avoid triggers such as certain foods, stress, sleep deprivation, medications, and environmental irritants
Hormonal regulation during menstrual cycles and careful timing of preventive drug therapies
Medication Overuse Headache
Occurs in response to withdrawal from prolong use of acute headache medications
Occurs when triptans are used more than 6 times a month and other analgesics used 3 or more times a day for 3–5 days a week
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Headache
Drugs for Acute and Migraine Headaches
Headaches caused by stress, tension, or neuralgia
Use non-narcotic or neuropathic pain medications
Migraine
Use acute abortive and chronic preventive treatments
Preventive therapy is needed if 2–3 migraines a month
Abortive treatment works best when started within minutes of the first symptoms
Preferably during the prodrome or aura phase
NSAIDs, ergotamine drugs, and corticosteroids are used if abortive therapies are not working
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Headache
Drugs for Migraine Headache: Triptans
Indication: first-line abortive therapy
Begin working in 15 minutes and last 2 to several hours
If severe throbbing pain had already started triptans are not as effective
Has limits on total number of doses or total dosage that patients can take every 24 hours
Mechanism of Action: stimulate serotonin receptors to cause vasoconstriction of cerebral blood vessels
Routes: all are oral; Zolmitriptan (Zomig) is also nasal; Sumatriptan (Imitrex) is also nasal and SC injection
Selective Serotonin Receptor Agonists (Triptans)
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Headache
Drugs for Acute Headache: Triptans (continued)
Side Effects (common): dizziness, hot flashes, tingling, chest tightness, muscle aches, weakness, increased blood pressure, and sweating
Side Effects (administered by injection): bruising sometimes occurs at the injection site
Cautions
Do not take if high blood pressure, heart disease, or angina
Do not take with MAOIs; could cause serotonin syndrome
Do not take with ergotamine
monoamine oxidase inhibitors (MAOIs)
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Headache
Drugs for Acute Headache: Combinations
Combinations of non-narcotic analgesics and caffeine are used to treat mild migraine headaches
Using analgesics from multiple classes attacks pain from different mechanisms due to synergistic drug therapy
Caffeine is sometimes combined with other analgesics
Improves pain control by constricting blood vessels, but to a lesser extent than triptans
Barbiturate products are controlled substances that are sometimes used for migraines
Examples: butalbital and butorphanol
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Headache
Drugs for Acute Headache: Combination Agents (continued)
Routes: all are oral, except butorphanol is nasal, IM and IV
Cautions (barbiturates, opiates)
Causes drowsiness and dizziness
Do not take with alcohol
Produce tolerance and dependence; may be habit forming
Recommend limited and short-term use
Caution (combination products with aspirin): do not take if allergic to aspirin or NSAIDs
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Headache
Drugs for Headache Prevention
Indication (preventive drug therapy): migraine affecting normal life and occurring more than twice a month
Drugs are taken daily or at regular intervals
Includes
Beta blockers
Antidepressants (tricyclics and serotonin reuptake inhibitors)
Anticonvulsants (valproic acid, topiramate, and gabapentin)
Calcium-channel blockers (verapamil and nimodipine)
NSAIDs
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Anesthesia
About Anesthesia
Indications: inhibits sensation and pain during procedures such as surgery, dental work, and colonoscopy
General anesthesia
Affects the entire body and loss of consciousness occurs
Skeletal muscle relaxes, breathing and cardiac function slows, and blood pressure decreases
Local anesthesia
Affects a select part of the body
Causes loss of pain, tactile sensation, temperature sensation
No loss of consciousness
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Anesthesia
About Anesthesia: Preanesthetic Medications
Indications: short diagnostic procedures or to enhance relaxation, pain control, and amnesia
Reduce patient anxiety and resistance to therapy
Medications: midazolam (Versed), diazepam (Valium), and lorazepam (Ativan), and fentanyl in various forms
Administration: systemical
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Anesthesia
General Anesthetics
Indications: surgery and other procedures requiring overall muscle relaxation to keep the patient still
Cause loss of consciousness
Nitrous oxide is the exception
Indication (nitrous oxide): dental procedures
Dosage Forms: inhaled and injectable
Length of Effect: varies, usually only a few minutes
Anesthesiologist or anesthetist administers and adjusts these medications throughout a procedure
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Anesthesia
General Anesthetics (continued)
Inhaled Anesthetics
Storage: steel containers as compressed gas or liquid
Administration: inhaled through a face mask
Most reduce blood pressure and renal function; concomitant IV fluids given to counteract this effect
Technicians do not handle these products
Injectable anesthetics
Administration: continuous infusion
Technicians in surgical satellites prepare these agents
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Anesthesia
General Anesthetics (continued)
Side Effects: nausea, vomiting, decreased blood pressure, and reduced renal function
Coadministration (during procedures): antiemetic medications and IV fluids counteract side effects
Cautions: do not use with seizure disorders
Caution (rare, life-threatening): malignant hyperthermia
Body temperature rises suddenly and rapidly with heart arrhythmias, difficulty breathing, and muscle rigidity
Technicians stock and maintain dantrolene to treat malignant hyperthermia; check expiration date
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Anesthesia
Local Anesthetics
Indications: dental work, stitches, and sutures
Dosage forms: topical, injection, and IV
Mechanism of Action: depress first the nerve activity of small axons, then that of larger myelinated nerve fibers
Esters are short-acting drug molecules metabolized by local tissue
Amides are longer-acting drug molecules metabolized by the liver
Side Effects: allergic reaction, skin rash, swelling at the application site, and CNS excitation, and cardiac arrhythmias
Caution: consult with prescribers if have seizure disorders
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42. Analgesic and Anesthetic Antagonists
Naloxone (Narcan)
Is an opiate receptor antagonist that counteracts opioid pain and preanesthetic medications
Indications: reverse opiate effects in overdoses
Flumazenil (Romazicon)
Is a benzodiazepine receptor antagonist
Indications: reverse excessive sedation, speed recovery of consciousness in overdoses, and manage overdose of benzodiazepines
Both agents given in the emergency or operating rooms
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Your Turn
Question 1: A patient has occasional migraine headaches. She would like a medication to quickly stop her migraines before they become severe. What is the physician likely to prescribe? Answer: The physician is likely to prescribe a triptan because they are the first-line drug therapy for aborting migraines. Question 2: A patient has a deep cut that will not stop bleeding. The cut will require some stitches. What type of anesthetic will likely be used before the procedure begins? Answer: A local anesthetic will be applied before the cut is stitched up.
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44. Herbal and Alternative Therapies
Caffeine
Is a CNS stimulant
Used in combination with other analgesics for headache, fatigue, and drowsiness
Capsaicin
Is a chemical derived from cayenne peppers
Used as a topical treatment for pain
Feverfew
Is a plant product
Used for migraine pain, menstrual cramps, and arthritis
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Summary
Non-narcotic medications such as aspirin, acetaminophen, or NSAIDs are the first-line treatment for pain
Narcotic medications are used for moderate or severe pain; they can promote tolerance and dependence
Triptans are the mainstay of abortive migraine treatment
General anesthesia involves a loss of consciousness and is either intravenous or inhaled
Local anesthesia results in a loss of sensation in a specific area of the body and is topical or injected
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